Method of forming electrical insulators



Feb. 28, 1928.

1,660,441 I. Q. GURNEE METHOD OF FORMING ELECTRICAL IN- ULATORS Filed Jan. 14, 1927 tion and do not exceed Laterr uurren stares Parser oer-res,

ISAAC Q; GURNEE, or BUTLER, new JERSEY.

METHOD or romaine nLEctrBIoAL ,Ins'UL'A'rons.

Application filed January 14, 1927'. Serial No. 163;,19'3'.

My invention relates to improvements in metliods'of forming insulation; especially insulation to be used for electrical appliances, and tobe produced by molding: into shape. An object of the invention isto provide a method of forming such insulation so as to give the exact dimensions and" configuration required topermit the insulation, when finished, to fit snugly and properly into the place intended to receive it. in thoe-leetrical device of which it is to be apart.

Anotherobj'ect of the invention' is to provide a method of forming such insulation in a manner that will prevent warping and deformation of every kind that would render the insulation unfit for service; I

Further objects and advantages of the invention will be made clear in the following description, taken with the" accompanying drawings, which illustrate the preferred mode of p *acticing the invention; but I of coursereservetlie right to-ma'ke such changes in the carrying out of my process as are embraced within the principlenof the inventhe scope of the appended claims. i

On said drawings Figure 1 is a front view;

Figure 2 a rear View, and

Figure 3 is aside View, partly in section, of a body of insulation made in accordance with my improved process, as it appears when completed; and

Figure 4 is a side View, partly in section,

similar to Figure 3, showing the insulation as it is formed in the stages prior to finishmg, to allow for cooling and contracting,

and thus. insure the final correct shape.

The same numerals identify the same parts throughout.

My invention 1s set forth here in connection with the insulation which carries the slip ring on the armature of a. high tension magneto of the type which supplies ignition current to internal'combustion engines; but obviously the invention can be practiced to form insulators for other electrical apparatus also. Such an insulator comprises a tubular body or neck 1 with a flange 2 at one end and a flange 3 at the opposite end; the flange 3 carrying an eccentric, axially extending boss 4. The face of the flange 3 is raised or presented in relief to some extent, as in dicated at 5. Encircling the relatively thickneck 1 between the relatively thin flanges 2 and 3 is the slip ring 6, upon which is to bear acontact brush, not shown, connected to the distributor of the magneto andlthc boss 4' has a passage 7 with an enlarged end 8. Through: the neck passes a bore 9. In practice, the bore 9 receivesthe'shaft' of the armature of the magneto, and the insulator is thus mounted to rotate with the aru'iatu re; The high tension winding on the armature can be united tothe ring" 6 by a conductor in the passage 7 of the boss 4.

. The insulator is usually mtid'eof rubber, and formed in a mold. To make the insua lat-or fit into'place properly 011 the armature of the magneto, and afford the desired in sulating effect, theinsulator must not only have the exact size required, but must also be of correct shape, with the opposite ends orfaces the flanges 2" and parallel to each other, and the boss-4 parallet to the axis of the bore9; If the interior of the mold has the surfaces which engage. the outer each other, so that the'insulator' has these two faces" or ends flat or plane, and normal 0 to the axis of the bore 9, when it is removed from the mold, it'is liable on" cooling: toco'm tract and shrink adjacent the two open ends of the bore 9, drawing the outer faces of the flanges 2 and 3 inward adjacent the bore, and thus making the opposite ends of the insulator concave. This warping or distortion constitutes a defect which renders the insulator entirely inserviceable.

To avoid such distortion, I mold the insulator in a deformed die which gives the insulator an initial shape that is shown in. Figure 4. The inside surfaces of the die which engage the outer faces of the flanges 2 and 3, or opposite ends of the insulator,

are made concave to a predetermined degree,

lating material fills the cavity of the niold and remains therein foran interval as long as necessary; for example ten minutes to one hour, the mold being heated during the entire period to the necessary extent, as by steam at from .50 to 200 lbs. pressure in contact with the exterior of the mold, which may be located at this stage in a suitable chamber. The insulator is then removed from the mold and subjected to a second, open heat in a vulcanizing device or chainher, for the necessary period, which may be several hours (such as 8 to 10) in length, at a somewhat lower temperature provided by steam at say 30 to 90 lbs. pressure. The insulator then becomes permanently set by contraction, the convexity of the two ends disappears, and is replaced by perfectly fiat, plane surfaces, as indicated in Figure 3, and the boss 4, no longer diverges, but becomes parallel to the axis of the bore 9. Thus all distortion is obviated without cutting away any part of the insulation, and the insulator gets its final correct shape without further working after leaving the mold, except the additional thermal treatment above de scribed.

By this procizss the insulators can be pro duced in large quantities, with the highest degree of certainty that they will effectually answer their intended purpose inactual practice under service conditions.

Of course any way of applying the heat may be followed since not only steam heat' can be utilized but dry heat as well.

Having described my invention, what .i.

believe to be new and desire to secure and protect by Letters Patent of the United States is r lrThe method of producing insulation which consists in forming the insulation first in a deformeddie, and then causing the insulation, after removal from the die, to take on its correct shape and dimensions by contraction.

2. The method of producing insulation which consists in giving the insulation a swelled out form in a mold which is subj ected to heat, and thenremoving the insulation from the mold and subjecting it to open heat to a diminished degree to allow the insulatioirt-o shrink into its finished shape and condition.

8; i The method of forming insulation that v tour, surfaces that are adjacent a thick. portion of the article. i

5. The method of moulding an article having a body and bearing a flange, out of material subject to shrinkage, which consists in initially forming the article with a convex surface upon the flange and adjacent said body so that such surface wi1l be flat after shrinkage.

In testimony whereof I aflix mysignature.

' ISAAC o. VGURNEEL 

